The invention relates to providing a dial-up connection in a packet radio system, particularly to a mobile station already having an active packet data protocol context.
In addition to circuit-switched services, packet-switched GPRS service (General Packet Radio Service) is also standardized in the GSM system, particularly for the transmission of IP data (Internet Protocol). A network supporting GPRS service comprises a gateway GPRS support node (GGSN) and a serving GPRS support node (SGSN). The SGSN serves mobile stations (MS) attached to the GPRS network in its service area, transmits and receives data packets from said mobile stations and monitors the location of the mobile stations in its service area. The attachment of an MS to a GPRS network and, more particularly, to the SGSN, refers to the formation of a mobility management context for the MS, this function in a GPRS network being GPRS Attach. The GGSN acts as a gateway between the GPRS network and an external packet data network (PDN). External data networks include another network operator's GPRS network, the Internet, an X.25 network or a private local area network, for example.
In order for packet-switched data to be able to be transmitted between a mobile station and a network, a PDP context (Packet Data Protocol) has to be activated for the mobile station. When a PDP context is activated, the MS is bound to a PDP address (IP address) used in communicating with external networks. This changes the PDP state of the MS to active (ACTIVE state). In the GPRS standard, an MS is composed of a terminal equipment part (TE) and a mobile termination part (MT). The MT and the TE may be located physically in the same wireless device or e.g. a laptop computer may constitute the TE and a wireless device the MT. If the MT and the TE are physically in different devices, a connection is set up between them before transmission of data in the applications comprised by the TE.
Since radio resources are only used when data is transmitted, a GPRS mobile station may always have a PDP context activated when attached to a network. Mobile stations may be arranged to automatically activate also the PDP context when attaching to the GPRS network. The MT may act as a modem from the point of view of the TE comprised by a physically separate device, such as a laptop computer. In this case, a dial-up connection may be provided for e.g. an e-mail application for data transmission over a wireless network to a company's Intranet. A PPP (Point to Point Protocol) link may be set up between the TE and the MT for the dial-up connection of an application comprised by the TE, allowing transparent data transmission over the GPRS network from the point of view of the TE application. A PPP link may also be arranged for a dial-up connection between a terminal and a network element, typically the GGSN, of the packet radio network.
However, according to prior art, an existing active PDP context cannot be utilized for a dial-up connection. Even though the mobile termination part supports several simultaneous PDP contexts, its processing resources and memory are unnecessary loaded. In addition, if charging is based on time, the user pays unnecessarily for two active PDP contexts.